Electric control system for induction machine containing winding elements of two wound rotor induction machines



United States Patent Fukuo Shibata. I3 'lokiwa-cho. Nishinomiym Hyogm Japan [2 I] Appl. No. 832,549

Filed May 21, 1969 Division ofSer. No. 624.119. Mar. 14. 1967, now abandoned.

[72] Inventor [45] Patented Dec. 22, 1970 [32] Priority Mar. 14. 1966; Mar. 31, I966 [33] Japan [54] ELECTRIC CONTROL SYSTEM FOR INDUCTION MACHINE CONTAINING WINDING ELEMENTS OF TWO WOUND ROTOR INDUCTION MACHINES 8 Claims, 3 Drawing Figs. [52] U.S.CI. 318/197, 318/45, 318/237 [51] Int. Cl. H02p 7/36 [50] Field ofSearch 318/4549, 50, I97, 225, 237

[56] References Cited UNITED STATES PATENTS 2,201,006 5/1940 Kilgore 318/197X 2,355,727 8/1944 Holters 3l8/I97X 3,327,189 6/1967 Hedstrom 318/237X Primary Examiner-Otis L. Rader Assistant Examiner-Gene Z. Rubinson ABSTRACT: In an induction machine arrangement which contains two stator windings and two rotor windings rotating mechanically together with each other, controlled rectifiers are connected electrically between terminals of the two rotor windings, and the controlled rectifiers are divided into two groups, the anodes and cathodes of one group being connected respectively to terminals of one rotor winding and to terminals of another rotor winding, and the anodes and cathodes of the other group being connected electrically respectively to the latter terminals and to the former terminals.

PATENTEUUECZEIQYB I 3549868 sum 1 or 2 Inventor ELECTRIC CONTROL SYSTEM FOR INDUCTION MACHINE CONTAINING WINDING ELEMENTS OF TWO WOUND ROTOR INDUCTION MACHINES This is a division of application Ser. No. 624,1 l9 filed Mar. 14, 1967, now abandoned. I

This invention relates to electric control system for induction machines. An induction machine is an asynchronous alternating current machine which comprises a magnetic circuit interlinked with two electric circuits, or sets of circuits, rotating with respect to each other and in which power is transferred from one circuit to another by electromagnetic induction. Examples of induction machines are induction motors, induction generators, and certain types of frequency converters and phase converters.

More particularly, the invention is concerned with the control system of speed for induction machines, such as induction motors, over a wide range by employing rectifiers. Further, theinvention is concerned with the control system for an induction machine operating as a generator by employing rectifiers.

In the control of induction machines by rectifiers, it is important to provide control systems by which the induction machines can be controlled as motors over wide speed ranges without sacrificing efficiency of operation, torque or economy of apparatus of the systems.

.I-Ieretofore, various arrangements have been devised which permit the control of induction motors by employing rectifiers which are electrically connected with the rotor or secondary windings of the induction motors. In general, the electric power taken from the rotor or secondary windings is either fed back to the AC source or fed to the main shaft of the induction motors. When it is fed back to the AC source, in the prior arrangements, torque or efiiciency of operation is not so large in case of comparatively low speedcontrol range, because a large part of the electric energy supplied on the input terminals of the induction motoris fed back to the AC source and is not converted into the mechanical torque.

When the electric power taken from the rotor is fed to the main shaft of the induction motor by using a direct current motor in the prior method, the efficiency of operation or economy of apparatus of the system is rather reduced.

It is one of the objects of this invention to provide a speed control system by which the induction machine can be controlled when acting as a motor over a wide speed range without sacrificing efiiciency of operation, torque or economy of apparatus of this system.

In the control of induction machines it is important to provide control systems by which the induction machines can be controlled as brushless type motors or generators. It is another object of this invention to make a brushless type controllable induction machine acting as a motor or a generator.

In the control of frequencies of generators it is important to keep constant frequencies of generators which are driven by prime movers at speeds not always constant. So, it is further another object of this invention to provide a simple control system keeping a constant frequency of a generator which is driven by a prime mover at speed not always constant.

It is still another important object ofthis invention to provide a speed control system of very simple construction by which the induction machine can be controlled over wide speed range without sacrificing efficiency of operation.

This invention possesses many'other advantages, and has other objects which may be made more clearly apparent from a consideration of several embodiments of this invention. For this purpose, there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of this invention, but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawingsi ii l FIGS. 1 and 2 are system diagrams illustrating different forms of this invention, the systems being adapted to utilize any multiphase or single-phase electrical energy, all represented by three-phase lines on these diagrams.

FIG. 3 is an example showing a construction according to this invention.

The machine arrangement according to the invention comprises the following combination: two alternating current electric windings called a first winding and a second winding which are coupled electromagnetically with respect to each other and rotating with respect to each other; other two alternating current electric windings called a third winding and a fourth winding which are coupled electromagnetically with respect to each other and rotating with respect to each other; controlled rectifiers which are inserted and connected electrically between the terminals of the said second winding and the terminals of the said fourth winding; an alternating current bus connected electrically with the terminals of the first winding and with the terminals of the third winding; means for rotating mechanically the said second winding together with the said fourth winding; wherein the said controlled rectifiers are divided into two groups, the anodes and cathodes of one group being connected respectively to the terminals of the second winding and to the tenninals of the fourth winding, and the anodes and cathodes of the other group being connected respectively to the terminals of the fourth winding and to the terminals of the second winding; further, two electric windings called a fifth and sixth windings are coupled electromagnetically with respect to each other; and the firing circuit which is connected to each gate or control element of the controlled rectifiers is supplied with signal electric power from the said alternating current bus through the said electromagnetically coupled fifth and sixth windings.-

In FIG. 1, two electric windings coupled electromagnetically with respect to each other are shown. These are; a first winding 1 and a second winding 2. These two windings l and 2 are coupled electromagnetically with respect to each other, and are arranged for rotating with respect to each other. Further, other two electric windings are shown in FIG. 1. These are a third winding 3 and a fourth winding 4. These two windings 3 and 4 are also coupled electromagnetically with respect to each other, and are arranged for rotating with respect to each other. The second winding 2 is in general em bedded in slots on a surface of a rotor. The fourth winding 4 is also generally embedded in slots on a surface of another rotor. A dotted line 5 shows that the second winding 2 rotates mechanically together with the fourth winding 4. That is; the rotor including the second winding 2 is mechanically coupled with the rotor including the fourth winding 4. The phrase to couple mechanically is herein defined as to connect the members so that the mechanical torque or power can be transferred between the members either with or without slip, for instance, by direct coupling (with bolt, pin etc.), a rubber coupling device or chain. We can consider an example of mechanical coupling between the rotor including the second winding 2 and the rotor including the fourth winding 4 as follows:

There are two induction machines 6 and 7 whose stationary windings are the first and the third wing windings (l and 3) respectively and whose rotor windingsare the second and the fourth windings (2 and 4) respectivelyz these rotors containing respectively the second winding 2 and the fourth winding 4 are coupled mechanically with each other, for instance by a direct coupling (with bolt, pin etc.) with gear or' chain.

In all these cases, the second winding 2 rotates mechanically together with the fourth winding 4. Controlled rectifiers 28 are connected electrically between the terminals of the second cally with the terminals of the third winding 3. When the alternating current bus 13 is supplied from an alternating current source, the first winding 1 and the third winding 3 are supplied with an alternating current fromthe alternating current source. The firing circuit 12 of each'gate 29 of the controlled rectifiers 28 is supplied with electric energy from the alternating current bus 13 through a phase shift control device 14 and an induction machine 15. This induction machine 15 consists of a stationary winding 16 and a rotor winding 17. Although the sixth winding l7 in some embodiments of this invention. These two electric windings l6 and 17 are coupled electromagnetically with respect to each other and are arranged for rotating with respect to each other. The stationary fifth winding 16 is connected electrically with the alternating current bus 13 through the phase shift control device 1 The rotary sixth winding 17 is connected electrically with the firing circuit 12. The sixth winding 17 is mechanically coupled with the fourth winding t. Therefore, the sixth winding 17 rotates together with the fourth winding 4. A dotted line 18 shows the mechanical coupling between the rotor of the fourth winding 4 and the sixth winding 17.

When the alternating current bus 13 is supplied with electric'energy from the alternating current source, the first winding 1, the third winding 3 and the fifth winding 16 are supplied with electric current from the alternating current bus 13. So, the rotating fields are produced in the stators and the rotors of these induction machines 6, 7 and 15. We can arrange so that the direction of the rotation of the rotating field made by alternating current flowing in the first polyphase winding 1 is opposite to the direction of the rotation of the rotating field made by alternating current flowing in the third polyphase winding 3. The directions of the rotation of the rotors of the second winding 2, the fourth winding 4! and the sixth winding ,17 aresame with respect to each other.

- sixth winding 17 is equal to that of the fourth winding 4. Thus the fourth winding 4 is supplied from the controlled rectifiers 28 having the same output frequency as the fourth winding 4.

The fourth winding 4 rotates in the third winding 3 in the region s(slip) l, so that the fourth winding 4'revolves against the rotating field, when the direction of the rotation of the rotating field made by alternating currentflowing in the third polyphase winding 3 is opposite to the direction of the rotation of the rotating field made by alternating current flowingin the first polyphase winding 1. In this case, the controlled rectifiers 28 work at a higher frequency than that of the alternating current bus 113.

Part of the slip power supplied from the controlled rectifiers 28 to the fourth winding 4 is fed back to the alternating current bus 13. A part of the electric power supplied from the alternating current bus 13 to the first winding 1 is converted into the mechanical power of the rotor containing the second winding 2, and another part of the electric power supplied from the alternating current bus 13 to the first winding l is fed to the fourth winding 4 through the second winding 2 and the controlled rectifiers 2%. Thus, the mechanical power of the rotor containing the fourth winding 4 can be added to the mechanical power of the rotor containing the second winding 2 when the induction machine set 6--7 operates as a motor. The mechanical power of the rotor containing the second winding 2 or that of the rotor containing the fourth winding 4 is converted from the electric power which is absorbed from the electric power flow between the first winding 1 to the third wintiing 3 through the second winding 2, the controlled .rectifiers ZB .and the fourth winding With'mechanical "and controlled rectifiers'power limitations, the device permits con;-

'tinuous speed control fromzero to the'maximum speed near to the synchronous speed of the second winding 2. The speed of the rotor of the second winding 2 rotating together with the fourthwinding 4 can be controlled by the control of the phase shift control device M.

The arrangement of F16. f2 is -alm'ostthe same as that-of FIG. 1, except that the phase shift control device .14 isinserted between the sixth winding 17 and the firing circuit 12 of the controlled rectifiers 28. Generally, the number of poles made by the first winding 1 must be the same as that made by the second winding 2,'and'-.the number of polesmade by the .t hird winding 3 mustbe the sameas that made by the fourth winding 4. I

When the first winding 1 is embedded in one stator and the third winding 3 is in'the other stator, and-furthen'the second winding 2 is embedded in onerotor andthe fourth winding 4iis in the'other rotor, if the direction of the rotation of the rotating field made by alternating current flowing in the third polyphase'winding 3 is opposite to the direction of the rotation of the rotating field made by alternating current flowing in the first polyphase winding 1, the number of poles made by .the first-winding 1 may be the same as or different from that made by the third'winding 3.

In FIG. l, the terminals 26 of the second winding 2 areconnected to the terminals 27 of the fourth winding 4 through eighteen controlled rectifiers 28. These controlled rectifiers are divided into two groups, the anodes and cathodes of one group being connected'respectively to the terminals of the second winding 2 andof the fourth winding-4, and the anodes trolled by means of a voltage supplied to the-controlgrid or gate. The control grids or gates of the individual rectifiersare supplied from the control unit 12 (or the firing circuit 12). A. phase shift'control device 14 is coupled electrically to thetcon-,.

troliunit (or firing circuit) 12 through the fifth winding 16. and; the sixth winding-l7 for the purpose of shifting the phase of the supplied grid(gate) voltages with respect to thealternat ing current supply in dependence upon a control signal'sup plied tothe phase shift control device 14.

Thusthe controlled rectifiers 28permit power to be fedinto the fourth winding 4 from the second winding 2, and. the, amount of power fed into the fourth winding 4'may be varied,

between almost zero and a maximum value by suitable varia-.

tion of the controlsignal. Control of the motor set 6-7 has i follows. The torque of the motor 6 is directly proportional to} the current flowing in the second winding 2, andthis current is clearlya function of the e.m.f. induced in the second winding,

2 andthe amount ofpowerfed into the fourth winding 4 from: the second winding 2. The amount of power fed from the; 1 second winding z to the fourth winding 4 is controlled by'thei, phase shift control device 14 in dependence upon thesupplied control signal so as to vary thefraction of eachcycle during.

which each rectifierconducts.

An importantadvantage of the arrangement of FIG. 1 is that, even a commutationfailure during feed of power will'not lead to a'short circuit because it is'restrictedto one phase of the;

rotor circuit, and the are which hasknotbeen extinguished dur;

tion with greater slip this time would be considerably'less,"

In FIG. 3 which is an example showing a construction according to this invention, the first winding 1 is on the surface of one stator core 37, the third winding 3 is on the surface of another stator core 39, and the fifth winding 16 is on the surface of still another stator core 41. The second winding 2 is on the surface of one rotor 38, the fourth winding 4 is on the surface of another rotor core 40, and the sixth winding 17 is on the surface of still another rotor core 42. In FIG. 3, these six kind of winding 1, 2, 3, 4, l6 and 17 are included in one case 35, and the three kind of windings 2, 4 and 17 are arranged for rotating around one shaft 36.

In FIG. 1, it is shown that the controlled rectifiers 28 and the firing circuit 12 form a unit which is connected electrically between the second winding 2 and the fourth winding 4. This unit can be either stationary or rotary. If it is installed in a static position outside the rotary part, it'is necessary to provide sliprings on the terminals of the second winding 2 and the fourth winding 4 for connecting these winding 2 and 4 with the unit. If the above unit is arranged for rotating together with the second, the fourth and the sixth windings 2, 4, 17, it is not necessary to provide sliprings on the terminals of these windings 2, 4, 17, as shown in FIG. 3. In FIG. 3, the controlled rectifiers 28 are mechanically clamped or coupled with the rotor shaft 36 around which the controlled rectifiers 28 are mechanically driven together with the second, the fourth and the sixth windings 2, 4, 17.

Until now, we have mainly considered that induction machines containing the first, second, third and fourth windings in this invention can be driven as motors or electric couplings. However, the induction machines in this invention can be used also as induction generators. If the rotor containing the second winding 2 is driven at a speed more than its synchronous speed by a prime mover, the induction machine 6 operates as an induction generator. In this case, the

' respect to each other; other two alternating current ch synchronous speed (r.p.m.) of the second winding 2 means the speed obtained from the following formula.

(r.p.m.)- p

where p is the number of poles of the first or the second winding, and f is frequency of the alternating current bus 13.

In this case, if the alternating current bus 13 is supplied with electric power from the other alternating current source, the exciting current of the induction machine 6 can be supplied from the alternating current source (not shown in the FIG.

If there is no alternating current source other than induction machines 6, 7 and 15, the exciting current of the induction generator 6 can be supplied from the third winding 3 through the alternating current bus 13. Ordinarily, the induction machine 7 is driven at a speed less than its synchronous speed, when the induction machine 6 operates as an induction generator. If the induction generator 6 is supplied with exciting current only from the induction machine 7, the frequency of the alternating current bus 13 can be controlled by the control of the phase shift control device 14.

The induction machine set shown in FIG. 3 can also be driven as an induction generator, which will be understood windings called a third winding and a fourth winding whit coupled electromagnetically with respect to each othe rotating with respect to each other; controlled rectifiersi are inserted and connected electrically between the tern of the said second winding and the terminals of the said f windings; an alternating current bus connected electr with the terminals of the first winding and with the tern of the third winding; means for rotatin mechanically thi second winding together with the said ourth winding; wk

the said controlled rectifiers are divided into two group anodes and cathodes of one group being connected re tively to the terminals of the second winding and to th minals of the fourth winding, and the anodes and cathot the other group being connected respectively to the tern of the fourth winding and to the terminals of the second ing; further, two electric windings called fifth and windings, are coupled electromagnetically with respe each other; and the firing circuit which is connected to gate or control element of the controlled rectifiers is su with signal electric power from the said alternating or bus through the said electromagnetically coupled fiftl sixth windings.

2. The combination as set forth in claim 1, in which ti duction machines are formed: one is formed by the first ing embedded in one stator and the second winding embi in one rotor, and the other is formed by the third windin bedded in the other stator and the fourth winding embr in the other rotor.

3. The combination as set forth in claim 1, in which th and third windings are polyphase windings; and the dirt of the rotation of the rotating field made by alternatin; rent flowing in the first polyphase winding is opposite tof the rotating field made by alternating current flowing third polyphase winding.

4. The combination as set forth in claim 1, in whic number of poles made by the first winding is same a made by the third winding.

5. The combination as set forth in claim 1, in whit numberof poles made by the first winding is different that made by the third winding.

6. The combination as set forth in claim 1, in which a shift control device is electrically connected between the winding and the firing circuit of the controlled rectifiers.

7. The combination as set forth in claim 1, in which a shift control device is electrically connected with the winding.

8. The combination as set forth in claim 1, in which th trolled rectifiers are mechanically coupled or clampet the rotor shaft around which the controlled rectifie: mechanically driven together with the second, the four! the sixth windings. 

